Iran erupted last Thursday. By Friday, the protests against the government, which began in Mashhad near the Afghan border, had spread to dozens of cities. So when we traveled on Saturday to a movie theater on Manhattan’s Lower East Side to see “Darkest Hour,” Gary Oldman’s portrayal of Winston Churchill, imagine the jarring dislocation when the theater’s previews included a trailer for an admiring documentary of Barack Obama’s foreign-policy making, “The Final Year.”